The present invention is a condensation process for the preparation of organofunctional-terminated polydiorganosiloxane polymers and organofunctional polydiorganosiloxane copolymers. The process comprises reacting a hydroxyl-terminated polydiorganosiloxane polymer with (1) an organofunctional chlorosilane end-blocker to form the organofunctional-terminated polydiorganosiloxane polymer or (2) a mixture of an organochlorosilane end-blocker and an organofunctional dichlorosilane to form a organofunctional polydiorganosiloxane copolymer. The process is facilitated by conducting it in the presence of an aqueous solution of hydrogen chloride, where the water is present in a stoichiometric excess in relation to the hydrolyzable silicon-bonded chlorine.
Organofunctional-terminated polydiorganosiloxane polymers and organofunctional polydiorganosiloxane copolymers, particularly where the organofunctional group is an alkenyl are finding increasing use as paper coatings. However, the use of these materials is limited by the costs of production associated with current processes. For example, current equilibrium processes result in the production of undesirable volatile cyclic species which must be stripped from the product using high temperature and reduced pressures. The present condensation process results in very low residual volatile cyclics, thus no stripping is typically required. Therefore, the present process is a simple one-step non-equilibrium process using readily available materials, thus reducing the cost of production of these organofunctional siloxane polymers and siloxane copolymers.
Several methods for the production of chlorine-terminated polydiorganosiloxane polymers are known. For example, it is known that the hydrolysis and condensation of diorganodichlorosilanes can result in a mixture of cyclicdiorganosiloxanes and short-chained chlorine end-terminated polydiorganosiloxanes, with the concurrent formation of hydrogen chloride.
Sauer, U.S. Pat. No. 2.421.653. issued Jun. 3, 1947, teaches that polydiorganosiloxanes can be equilibrated with organodihalosilanes in the presence of an aqueous hydrogen chloride solution to form chlorine end terminated polydiorganosiloxanes.
Hyde et al., U.S. Pat. No. 2,779,776, issued Jan. 29, 1957, teaches that polydiorganosiloxane polymers can be equilibrated in the presence of an aqueous solution of hydrogen chloride to form chlorine-terminated polydiorganosiloxanes. Furthermore, Hyde et al., teaches that the chain length of the chlorine-terminated polydiorganosiloxanes is a function of the hydrogen chloride concentration in the aqueous phase.
These chlorine-terminated polydiorganosiloxane polymers can be further hydrolyzed with excess water to form hydroxyl-terminated polydiorganosiloxane polymers suitable for use in the present process.
In a first embodiment of the present process, a hydroxyl-terminated polydiorganosiloxane polymer is reacted with a organochlorosilane end-blocker containing at least one organofunctional substituent. The resultant product is an organofunctional-terminated polydiorganosiloxane polymer.
In a second embodiment of the present process, a hydroxyl-terminated polydiorganosiloxane polymer is reacted with a mixture comprising an organochlorosilane end-blocker and an organofunctional dichlorosilane. The resultant product is a block copolymer comprising diorganosiloxy blocks and organofunctionalsiloxy blocks.
The cited art does not recognize that hydroxyl terminated polydiorganosiloxane polymers can be reacted, as described in the present process, to form organofunctional terminated polydiorganosiloxanes and organofunctional polydiorganosiloxane copolymers